Avoiding pollution by HF catalyst residues

ABSTRACT

A used HF catalyst rerun unit comprises in tandem at least two strippers, a first to remove substantially all readily vaporizable components, e.g., light hydrocarbons and HF, and to separate acid-soluble oils as a liquid residue, and a second to produce rerun HF vapors and a stream of water containing HF. In an alkylation of a hydrocarbon operation, e.g., an isoparaffin by an olefin, said stream is used by reaction with an olefin to produce alkyl fluoride which can be fed to the alkylation reaction. Either before or after such reaction the stream is used to remove from noncondensible gas, as in a vent gas absorber, HF vapors therein contained and the stream returned to the HF rerun unit.

United States Patent [1 Carter 51 May 27, 1975 AVOIDING POLLUTION BY HFCATALYST [73] Assignee: Phillips Petroleum Company,

Bartlesville, Okla.

[22] Filed: Aug. 28, 1973 [21] Appl. No.: 392,233

[52] US. Cl 260/653.6; 260/68348 [51] Int. Cl. C07c 17/08 [58] Field ofSearch 260/683.48, 653.6

[56] References Cited UNITED STATES PATENTS 2,832,812 4/1958 Belden260/6536 Primary ExaminerD. Horwitz [57] ABSTRACT A used HF catalystrerun unit comprises in tandem at least two strippers, a first to removesubstantially all readily vaporizable components, e.g., lighthydrocarbons and HF, and to separate acid-soluble oils as aliquidresidue, and a second to produce rerun HF vapors and a stream of watercontaining HF. In an alkylation of a hydrocarbon operation, e.g., anisoparaffin by an olefin, said stream is used by reaction with an olefinto produce alkyl fluoride which can be fed to the alkylation reaction.Either before or after such reaction the stream is used to remove from:noncondensible gas, as in a vent gas absorber, HF vapors thereincontained and the stream returned to the HF rerun unit.

8 Claims, 1 Drawing Figure AVOIDING POLLUTION BY HF CATALYST RESIDUESThis invention relates to the recovery of HF normally unavoidablyyielded from a process employing the same as a catalyst. It also relatesto a method for the recovery of HF from noncondensibles normally yieldedfrom a process employing HF as a catalyst. Further, the inventionrelates to an improved alkylation operation, e.g., alkylation ofisoparaffin with an olefin wherein normally yielded HF is recovered fromnoncondensibles, converted, and returned for reuse in the process.

In one of its concepts, the invention provides a process forregenerating HF containing a hydrocarbon, acid-soluble oil, some waterand other impurities which comprises in a first zone separating bystripping with a hydrocarbon vapor all readily vaporizable HF thus toobtain an acid-soluble oil containing residue, treating overhead HF andhydrocarbon thus obtained under refluxing conditions to obtain asubstantially purified HF and hydrocarbon stream and condensed watervapor containing HF. In another of its concepts, the invention providesa process as is in the alkylation of hydrocarbons, for example, anisoparaffin with an olefin, e.g., isobutane and/or isopentane, withethylene and/or higher molecular weight olefins such as propylene, abutylene, and amylene or a hexylene, wherein the alkylation is conductedin the presence of HF catalyst, as known in the art, wherein the HFcatalyst is rerun as herein described and wherein the resulting water-HFstream obtained is caused to react with an olefin, e.g., as above named,to produce an alkyl fluoride phase which is passed to an alkylationreaction, for example, the original alkylation reaction or a subsequentone.

In a further concept, the water-HF from the stripping is used asdescribed herein to absorb HF from noncondensible gases and returned tothe stripping. Either before and/or after such use the water-HF from thestripping is contacted with olefin to form fluoride which is recoveredand used in the alkylation zone.

This invention will now be described with respect to an alkylationoperation. It will be clear to one skilled in the art in possession ofthis disclosure having studied the same that the invention possessesapplicability and adaptability to and in other operations in which HFcatalyst is employed.

Pollution f the air with HF acid vapor and light hydrocarbons occurswhen noncondensible gas is vented from, say, a depropanizer accumulatoras known in the art. The venting is continuous. The vent gas heretoforehas been neutralized in a closed system with, say, sodium or potassiumhydroxide or otherwise chemically contacted with an agent of which asuitable disposition must be made. In any event, however the HFcontaminating the vent gas has been recovered there has been a disposalproblem as in disposing of spent caustic combined with fluoride and aconcomitant waste of the HF.

I have now conceived a process for recovering HF contained in such ventgases. l have also discovered a process for generating. in situ. in thealkylation operation, in which HF catalyst is rerun or regenerated, areaction medium which can be used as absorbent for recovering from thevent gas the HF normally contained therein.

Thus, I have conceived that by operating the conventional HF-acid rerunoperation in two stages, a first in which acid-soluble oil is removed bysubjecting the used HF to stripping with a hydrocarbon, e.g., hotisobutane, and a second in which the recovered HF and isobutane streamis refluxed to obtain a substantially purified HF-isobutane stream, Ican obtain a water stream containing HF which can be used for a reactionwith an olefin, e.g., as herein named, to generate an alkyl fluoridecontaining stream or phase which is then passed to the originalalkylation or to a subsequent alkylation reaction or otherwise utilizedin the process. Thus, the water containing HF is used as absorbent toscrub vent gas emanating from the process thus enriching still furtherthe water with HF, which has now been removed from the vent gases whichcan, therefore, be vented safely, or can be used as a fluoride-free fuelgas following which this enriched water is reacted with an olefin toproduce a stream containing alkyl fluoride which by its furtherutilization retains, in situ, in the system, the HF.

It is an object of this invention to avoid atmospheric pollution in theventing of gases containing HF. It is another object of this inventionto provide for the recovery from vent gases of HF contained therein. Itis a further object of the invention to provide an improved alkylationoperation wherein HF is used as a catalyst and there are obtained gaseswhich are noncondensible and which normally, if vented, would causepollution of the atmosphere. It is a further object of the invention toproduce a fuel gas free from HF. A still further object of the inventionis to economically operate an HF catalyzed reaction by reducing loss ofHF therefrom.

Other aspects, concepts, objects and the several advantages of theinvention are apparent from a study of this disclosure, the drawing andthe appended claims.

According to the present invention, a used HF catalyst is stripped witha hot stripping vapor thus to obtain therefrom a heavy liquid residue,e.g., catalyst or acid soluble oil, and a stream containing HF,stripping vapor and water vapor, said stream is then subjected torefluxing conditions to obtain therefrom substantially purifled HF andstripping vapor and a condensed stream of water containing HF which thenis caused to react with an olefin to produce an alkyl fluoridecontaining stream, which is recovered and utilized in the HF catalyzedoperation.

Also, according to the invention, the stream of water containing HF canbe used directly to absorb HF vapors from vent gases and returned tosaid refluxing conditions and, as desired, either before or after saidreturn contacted with an olefin to formalkyl fluoride, thus to produce astream containing a lower HF.

Further according to the invention, there is provided a process for thealkylation of an alkylatable material with an alkylating agent employingHF as a catalyst wherein the water containing HF, the water having beenintroduced with the feedstocks, is obtained upon rerun of the used HFcatalyst. and the alkyl fluoride obtained, as described herein, is usedeither in the original or a subsequent alkylation step.

Given the foregoing description, one skilled in the art having studiedthe same can determine by mere routine testing the design and conditionsof operation required to carry out the invention. However, to more fullydescribe the invention and to set forth the now best mode 3 contemplatedfor it in its application to an alkylation operation, reference is hadto the drawing.

For sake of convenience, three sections of the drawing have been framedand these are termed A, B, and C. Generally, A represents but formodifications owing to the invention being described herein aconventional isobutane-olefin alkylation in which'are present aconventional isostripper and HF or propane recovery column. 8 representsan HF acid rerun unit according to the invention and C represents a ventgas scrubbing operation which is operated in conjunction with A and B.

lsobutane and olefin are fed to the system by l and 2. Recycle isobutanefrom 3 is combined with the isobutane feed and passed through 4 togetherwith olefin from 2 by 5 into riser-reactor 6 wherein it is intimatelycontacted with a stream of'HF catalyst as known in the art. Catalyst isnormally cycled from settler '7 by 8, 9, cooler 10, and a back to thesettler. Reaction for the most part takes place in riser-reactor t). insettler 7 there are formed a supernatant hydrocarbon phase passed byll'to an isostripper 12 while the lower phase consisting of used HF acidis cycled as described.

The operation of isostripper i2 is conventional in this description inthe sense. that there are removed as bottoms by it?) an alkylateproductcontaining stream, by 1 a normal butane containing stream, andoverhead at T5 to cooler-condenser to a vaporous stream containingprincipally HF vapor, propane, and noncondensibles. Stream 15 now cooledas far as possible with ordinary cooling water available in the plant ispassed by 17 to accumulator 18 from which a hydrocarbon phase formedispassed in part as reflux to the isostripper by 3.9 and in yieldquantities by 20 to HF column 21. An acid phase 22. is recycled 'bypassage by 23 into the upper portion of settler 7.

The isostripper and the HF column are reboiled as shown and asconventional in the art.

Bottoms stream 8 from the tower 2i. constitute essentially propanesubstantially free from HF. Overhead 25 is passed from column 21 to thecooler-condenser l6 and thus recycled to accumulator 18. Gases, notcondensed,p'ass by 26 into zone C.

In zone C there are provided a scrubber 30, a reactor 64-, and a settler31.

According to the present invention, as now described, scrubber 30 issupplied with a scrubbing or absorption medium from zone B. Thescrubbing medium is enriched in HF in zone C and the enriched medium isused in reactor 64 to produce alkyl fluoride.

A portion of the acid passes from the foot of settler 7 by to stripper3b. The stripper is heated and reboiled by hot isobutane vapors enteringat 37 as well as by conventional reboiler 70. The used HF catalyst isstripped by countercurrent contact while it passes downwardly againstthe rising isobutane vapors in a manner and under conditions such thatsubstantially 'only an acid-soluble oil residue is withdrawn at 38. HF,

hydrocarbon vapor and water vapor, according to the invention, passoverhead at 39 into a second stripper 40 which is refluxed with some ofits own condensed over head passed by 4i through condenser 42 and by 43into a top portion of the column 40. Column 40 is reboiled by heating aportion of the bottoms stream. comprising water and HF withdrawn at Mand passed by 45 to heater do and by 47 into the bottom of column 40.Yield quantities of Water and HF are taken by $8 into the top ofscrubber 30 in section C. The point of entry of the water containing HFstream is selected to obtain the best or optimum desired scrubbingconditions so that gases vented from the system at 50 will besubstantially free from HF. As shown, the absorbing medium entering at49 is withdrawn at 51 and can be cycled by 52 to 49 and thence into thetop portion of scrubber 30. There can be added directly to scrubber 30,as desired, additional scrubbing medium, for example, additional water;or, additional water can be introduced at 53 into the cycling stream 52.

y The bottoms 51 are passed to reactor 6 to which also is passed, inthis embodiment, a portion of the olefin stream 2 fed to the process.Thus, olefin is fed by 54 into reactor 64 wherein a reaction between theolefin and HF in the water containing the same takes place. Phases areformed in settler 3i and a lower water phase removed at 55 is cycled toreactor 64 and/or by 56 and 57 to 48 and thence to the scrubber.Conditions are chosen in reactor 64 such as to substantially deplete thewater phase of HF. To this end a series of countercur; rently operatedcontactors can be employed in lieu of a single reactor as shown via 64.Liquid water accumulating in the system is removed at 58 and 7317 fromthe process. This water will be only that water which together with theamount of water vapor emanating at 50 equals the Water introduced intothe system via the feedstocks. This relatively small quantity of waterwill now be treated as may be desired before it is discarded. Alkylfluoride from 31 is passed to the alkylation reactor a by'SSA, 62, and5.

ln Ser. No. 327,734 filed Jan. 29, 1973, by me there is described andclaimed a process and apparatus for contacting a hydrogen fluoridecontaining vapors stream with a water stream to form a first mixture,reacting the first mixture with an olefin stream under conditionssufficient to form an alkyl fluoride and recovering an alkyl fluoride.The disclosure of this copending application is incorporated herein byrefer ence.

In the application conditions for the reaction in reactor 64 are given.The said conditions are now preferred.

Briefly, in reactor 64 there will be maintained a temperature in therange of from about 50 to about 150F, preferably from about to about 110F, at a pressure not, substantially greater than about 300 pounds persquare inch gauge. The olefin to HF weight ratio in the reactor will befrom about 5 to l to about 5 to 2, and in any event such as to react outthe HF from the HF- water extract or absorbent stream. Now preferred isa concentration of HF of 20-30 percent in the reaction mixture of HF,olefin. and water.

Depending upon the alkylation operation, in connection with which thedrawing has been described as a specific example, the olefin in reactor64 will be, preferably, isobutylene but can be and/or include any one ofpropylene. a normal butylcne, an amylene, hexylene, etc. Specificexamples of butylenes are butene-l. cisbutene-Z, and trans-butcne-Z.Although the olefin can be added as a vapor or as a liquid or evencontained in a suitable solvent or diluent, it is now preferably addedas such in the liquid form.

While the absorber 30 conditions can be determined by more routinetesting by one skilled in the art in pos session of this disclosurehaving studied the same, the conditions given in said copcndingapplication are now preferred and. briefly. are a temperature in therange of from about 50 to about F. preferably from about 90 to about 1F, a pressure not substantially in excess of from about 300 psig,preferably about 150 to 200 psig, and the mol ratio of aqueous phase tomols of HF will be usually in the range of from about 3 to l to about 5to 1. Usually the pressure will beoptimum for good absorption and forfeeding the gases to a fuel line system. It is desirable to maintain theconcentration of HF in the HF-water extract or absorbent medium aboveabout weight percent, more preferably about weight percent up to about50 weight percent. The specific conditions in area B of the drawing canbe determined by one skilled in the art in possession of this disclosurehaving studied the same by routine calculations given the resultingstreams he is to obtain.

Presently, the following conditions are now considered applicable andpreferred. The pressure in stripper 36 will be approximately 25 poundsper square inch gauge albeit pressures in the range of from about 0 to 6220 to 260F. The kettle temperature of stripper will be approximately200240F while the overhead temperature will be approximately 160 to200F. Broader operating temperature ranges are applicable 5 and in agiven case such temperatures might be as much, more or less by F or so.importantly, depending upon the stripping medium, concentration ofimpurities, water present, and other factors which one skilled in theart of stripping fluids will take into ac- 0 count the conditions givenhere will be found to be entirely satisfactory.

The following calculated example further illustrates the invention asapplied in a specific instance, as discussed in connection with thedrawing.

EXAMPLE Alkylate Production (unit size), BPD 4000 about 50 pounds persquare inch gauge can be emlsobutane/Olefin Reactor Feed volume ratio13.0 ployed. The stripping isobutane, at these pressures, will 20 2 12:a: ggg Per 69 have a temperature ofapproximately 250F, the kettle v llmbumnc consumed/Unit volume temperature of the stripper 36 will beapproximately eBhR/IOOO BM Alkylate v 315cm 320}: while the Overheadwill be approximately HF Acid in rerun bottoms. Lbs/Bbl Alkylate 0.0546

TABLE I Calculated Plant Material Balance in Barrels Per Day Stream No.11 2 1 8 l3 l4 I5 35 37 38 48 50 Acid Rcrun Vent Propane Gaseous Chg.Strip- Acid Gus lso- Recycle (Kettle Oh to ping Soluble Scrub- Streambutane ()lel'in lso- Col. Alk v- Normal Col. Rerun lso- Oil Hlher Name:Makeup Feed butane 2| late Butane l2 Unlt butane Product Water ResidueConstituents: Ethane I .l 1 3 Propylene J62 Propane 7 307 4042 458 l6 l6lsobutane Z031 541 28047 3 9 (1.2 150 n-Butaue 7*) 21b |42l 2H) 5.7llutenes I l I I2 Pentcnes 293 i & n ix 227 1. 5) 4227 (H lsobutylFluoride 0. 420 0.6

HF Water Acid Soluble 4 Trace 0.6 Oil 7 l4 l3 .2Il7 3601 34am 4M 4525(1.0 19.2 5l3 150 13 1.2 19 Temperature J0 Qt) llll l ll'l ltll) H10 90250 3l5 23(1 90 Pressure 300 300 .ltltl 250 250 250 250 250 l5 l5 5set-um ml; 5| 5: 54 54 m s5 57 58A 62 to H Alkyl Alkyl \'ent(ias Recycle()lelin ()lelin Recycle Fluoride Fluoride Recycle Absorbent Water to toto Water Recycle Returnlrom Return front Water to Vent First Second toWater Flrst Second V to PUl'lll C(l Stream Reactor (his Reactor ReactorReactor from Reactor- Reactor- Second Acid Name: 04 Absorber 04 no b4Settlcr Settler Scttler Reactor Returned Constituents:

Ethane Propylene lo 48 lo 4t: Propane 5 l5 5 M lsobutane 27 9 .Z sll-Butane 4 l2 4 I- Buteues I81 50 17.7 53.4 Penteucs 5 I5 I 5 L: la: n& -t 3." ll 1 1- lsobulyl z; l 3.-

. l ill l\',ll (15 7.8 7.8 m Ho 419.4 Water Z-Hl l 5 p 23.4 23.4 0.4 l lt "4,4 Acid Soluble i z I l (m l -13 o to ill 5 la; 317' ill. all Isa?(12.!) Milt i )ll Ill ill I )ll lll )ll 90 )(I )ll )0 l I 'tl llII' lJno 17'' 15H 15H 25 2 325 25 25 5 The example shows that essentially 100weight percent of the hydrogen fluoride normally lost in vent gas andacid rerun bottoms can be recovered using this invention. In consideringthe hydrogen fluoride consumption one should consider that combinedfluorides will exist in the alkylate, propane and normal butane. Theselosses plus any inefficiencies in vent gas and acid-soluble oilstripping, plus the probability of the feed being occasionallywater-wet, will create conditions under which excess hydrogen fluoridewater must be released from the unit requiring hydrogen fluoridemake-up. The hydrogen fluoride recovery can be increased by operating ata percent hydrogen fluoride content in the fluoride reactor rather thanthe now preferred percent. Operation at a 20 percent hydrogen fluoridecontent will, however, require a higher olefin charge rate due to thelower conversion levels at this lower hydrogen fluoride content. Thesystem is operable in a range of about 20 to weight percent hydrogenfluoride in the reactor. At the upper limit, solubility of the fluoridesin the water phase becomes excessive below 20 percent hydrogen fluorideand conversion in a single pass becomes quite low.

While the alkylation of isobutane has been described, the isoparaffincan also include or be isopentane or other low boiling isoparaffin.

While the specific embodiment herein shown as described the water-HFstream from the vessel 30 is admixed under fluoride forming conditionswith olefin whereafter the HF depleted water, from which any unreactedolefin and fluoride have been removed, is discarded at 58, it is withinthe scope of the invention to return the water from the vent gasscrubber, enriched in HF to the stripper 40. It is also within the scopeof the invention to a priori react the HF in the water-HF from thevessel with olefin to form therein and to take therefrom fluoride priorto using said above treated stream in vent gas absorber 30. Thus at 51ait is possible to remove the HF water used in the vent gas absorber fromthe system into reactor 60 there is fed at least a portion of thewater-HF from 44 and therein the HF is reacted with olefin added from 54by 61. One

skilled in the art will, of course, operate the various portions of theprocess to achieve desired functions. For example, the water containingHF passing to absorber 30 must be of a concentration of HF of a quantityand of a temperature such that loss of HF from the absorber issubstantially completely avoided. Now preferred is a concentration of HFsuch that when the water is used there will be no appreciable loss of HFwith the vent gases and the bottoms 51 will contain less than about 50percent HF in the water removed from Reasonable variation andmodification are possible within the scope of the foregoing disclosure,the drawing and the claims to the invention the essence of which is thata hydrogen fluoride catalyst rerun operation is so conducted as toobtain in at least two stripping stages a rerun or purified streamcontaining HF and hydrocarbon and a water and HF stream which issuitable for absorbing from noncondensible gases HF vapor containedtherein thus to recover the same within the operation in which generatedfollowing which the HF in the enriched absorbing medium is converted toalkyl fluorides by reacting an olefin therewith, the alkyl fluoridesbeing suitable for use as in an alkylation reaction, alternative, if notdiscarded the used water-HF stream is returned to the stripping withouta priori reaction to form fluorides with the HF therein and then, in onemodification of this variant, is now under fluoride forming conditionsreacted with olefin, fluoride removed therefrom and then the thus heatedstream is used to absorb from noncondensible gases the HF- vaporcontained therein.

I claim:

1. A process in which a used HF acid alkylation catalyst is treated intwo stages to recover the HF values and react recovered HF with olefinsto obtain alkyl fluorides which process comprises the steps of:

a. contacting used HF acid catalyst in a first stage stripping zone witha hot hydrocarbon stripping medium under conditions sufficient to forman overhead stream comprising HF, water vapor and hydrocarbon strippingvapor and yield a heavy liquid residue of acid-soluble oil,

b. passing said overhead stream to a second stage stripping zoneoperated under refluxing conditions to produce a second overhead streamcomprising HF and hydrocarbon stripping medium and a bottoms streamcomprising condensed water containing HF, and

c. reacting said bottoms stream comprising condensed water containing HFwith an olefin under conditions to form an alkyl fluoride.

2. A process according to claim 1 wherein the used catalyst mass resultsfrom an alkylation of an isoparaffin with an olefin, the watercontaining HF is used to absorb HF from gases being vented from thealkylation operation following which the thus-enriched water containingHF is reacted with an olefin to produce alkyl fluoride useful in theprocess of alkylation.

3. A process according to claim 2 wherein in an alkylation of anisoparaffin with an olefin the hydrocarbon phase separated from thealkylation effluent is fractionated to recover therefrom HF acid, lightliquefiable hydrocarbons and a vent gas consisting principally of gaseslighter than propane and containing some HF vapor, the gases arecontacted under absorption conditions with said bottoms stream obtainedin step (b) comprising water containing HF to absorb HF from said ventgas, and then bringing together the thusenriched water containing HF andan olefin under alkyl fluoride producing conditions, obtaining an alkylfluoride containing phase and passing said phase to said alkylation ofan isoparaffin with an olefin.

4. A process according to claim 3 wherein the olefin in the alkylfluoride producing reaction is at least one selected from propylene,butene-l cis-butene-Z, transbutene-Z, isobutylene. an amylene, and ahexylene, the isoparaffin is a low boiling isoparaffin, e.g., isobutaneand/or isopentane, the vent gases originate from a fractionation inwhich these gases are separated from pro pane and heavier hydrocarbons,and the alkyl fluoride producing conditions include pressures up toabout 300 psig, a temperature in the range of from about to about l50F,and the olefin to HF weight ratio is in the range of about 5 to l toabout 40 to l.

S. A process according to claim 1 wherein the stripping medium entersthe first stage stripping zone at a temperature of about 250F, there ismaintained a kettle temperature in the first stage in the range of fromabout 3l5 to 320F. an overhead temperature in the range of from about200 to about 260F, and in the second stage stripping zone a kettletemperature in the approximate range of from about 200 to 240 F and anoverhead temperature of from about 160 to about 200F.

6. A process according to claim wherein the stripping medium is a lowboiling isoparaffin and the used catalyst results from the alkylation ofa low boiling isoparaffin with an olefin.

7. A process according to claim 6 wherein said isoparaffin is isobutaneand said olefin is isobutylene.

8. In a process for the alkylation of an isoparaffin with an olefin inthe presence of an HF acid catalyst to produce an alkylation effluentwhich is separated into a used HF acid phase and a hydrocarbon phase andthe hydrocarbon phase is fractionated to recover an alkylate therefromand a vent gas stream comprising gases lighter than propane andcontaining some HF vapor and further wherein the catalyst phase istreated in two stages to recover the HF values in water and therecovered HF in water is used as an absorption medium for recovering HFfrom the vent gases, the steps of:

a. contacting said used HF acid catalyst phase in a first stagestripping zone with a hot hydrocarbon stripping medium under conditionssufficient to form an overhead stream comprising HF, water vapor andhydrocarbon stripping vapor and yield a heavy liquid residue ofacid-soluble oil,

b. passing said overhead stream to a second stage stripping zoneoperated under refluxing conditions to produce an overhead streamcomprising HF and hydrocarbon stripping medium and a bottoms streamcomprising condensed water containing HF,

c. passing said bottoms stream to an absorption zone and thereincontacting same with said vent gases under conditions to remove HF fromsaid vent gases and yield an HF-enriched water-containing HF stream,

d. passing a portion of said HF-enriched watercontaining HF stream to areaction zone and therein contacting same with an olefin underconditions to produce alkyl fluoride,

e. passing the remainder of said HF-enriched watercontaining HF streamto said second stripping zone to remove at least some of the HFtherefrom, and

f. contacting at least a portion of the bottoms stream comprising watercontaining HF removed from said second stripping zone in a reaction zonewith an olefin under conditions which will produce an alkyl fluoride.

1. A PROCESS IN WHICH A USED HF ACID ALKYLATION CATALYST IS TREATED INTWO STAGES TO RECOVER THE HF VALUES AND REACT RECOVERED HF WITH OLEFINSTO OBTAIN ALKYL FLUORIDES WHICH PROCESS COMPRISES THE STEPS OF: A.CONTACTING USE HF ACID CATALYST IN A FIRST STAGE STRIPPING ZONE WITH AHOT HYDROCARBON STRIPPING MEDIUM UNDER CONDITIONS SUFFICIENT TO FORM ANOVERHEAD STREAM COMPRISING HF, WATER VAPOR AND HYDROCARBON STRIPPINGVAPOR AND YIELD A HEAVY LIQUID RESIDUE OF ACID-SOLUBLE OIL, B. PASSINGSAID OVERHEAD STREAM TO A SECOND STAGE STRIPPING ZONE OPERATED UNDERREFLUXING CONDITIONS TO PROUDCE A SECOND OVERHEAD STREAM COMPRISING HFAND HYDROCARBON STRIPPING MEDIUM AND A BOTTOMS STREAM COMPRISINGCONDENSED WATER CONTAINING HF, AND C. REACTING SAID BOTTOMS STREAMCOMPRISING CONDENSED WATER CONTAINING HF WITH AN OLEFIN UNDER CONDITIONSTO FORM AN ALKYL FLUORIDE.
 2. A process according to claim 1 wherein theused catalyst mass results from an alkylation of an isoparaffin with anolefin, the water containing HF is used to absorb HF from gases beingvented from the alkylation operation following which the thus-enrichedwater containing HF is reacted with an olefin to produce alkyl fluorideuseful in the process of alkylation.
 3. A process according to claim 2wherein in an alkylation of an isoparaffin with an olefin thehydrocarbon phase separated from the alkylation effluent is fractionatedto recover therefrom HF acid, light liquefiable hydrocarbons and a ventgas consisting principally of gases lighter than propane and containingsome HF vapor, the gases are contacted under absorption conditions withsaid bottoms stream obtained in step (b) comprising water containing HFto absorb HF from said vent gas, and then bringing together thethus-enriched water containing HF and an olefin under alkyl fluorideproducing conditions, obtaining an alkyl fluoride containing phase andpassing said phase to said alkylation of an isoparaffin with an olefin.4. A process according to claim 3 wherein the olefin in the alkylfluoride producing reaction is at least one selected from propylene,butene-1, cis-butene-2, trans-butene-2, isobutylene, an amylene, and ahexylene, the isoparaffin is a low boiling isoparaffin, e.g., isobutaneand/or isopentane, the vent gases originate from a fractionation inwhich these gases are separated from propane and heavier hydrocarbons,and the alkyl fluoride producing conditions include pressures up toabout 300 psig, a temperature in the range of from about 50* to about150*F, and the olefin to HF weight ratio is in the range of about 5 to 1to about 40 to
 1. 5. A process according to claim 1 wherein thestripping medium enters the first stage stripping zone at a temperatureof about 250*F, there is maintained a kettle temperature in the firststage in the range of from about 315* to 320*F, an overhead temperaturein the range of from about 200* to about 260*F, and in the second stagestripping zone a kettle temperature in the approximate range of fromabout 200* to 240* F and an overhead temperature of from about 160* toabout 200*F.
 6. A process according to claim 5 wherein the strippingmedium is a low boiling isoparaffin and the used catalyst results fromthe alkylation of a low boiling isoparaffin with an olefin.
 7. A processaccording to claim 6 wherein said isoparaffin is isobutane and saidolefin is isobutylene.
 8. In a process for the alkylation of anisoparaffin with an olefin in the presence of an HF acid catalyst toproduce an alkylation effluent which is separated into a used HF acidphase and a hydrocarbon phase and the hydrocarbon phase is fractionatedto recover an alkylate therefrom and a vent gas stream comprising gaseslighter than propane and containing some HF vapor and further whereinthe catalyst phase is treated in two stages to recover the HF values inwater and the recovered HF in water is used as an absorption medium forrecovering HF from the vent gases, the steps of: a. contacting said usedHF acid catalyst phase in a first stage stripping zone with a hothydrocarbon stripping medium under conditions sufficient to form anoverhead stream comprising HF, water vapor and hydrocarbon strippingvapor and yield a heavy liquid residue of acid-soluble oil, b. passingsaid overhead stream to a second stage stripping zone operated underrefluxing conditions to produce an overhead stream comprising HF andhydrocarbon stripping medium and a bottoms stream comprising condensedwater containing HF, c. passing said bottoms stream to an absorptionzone and therein contacting same with said vent gases under conditionsto remove HF from said vent gases and yield an HF-enrichedwater-containing HF stream, d. passing a portion of said HF-enrichedwater-containing HF stream to a reaction zone and therein contactingsame with an olefin under conditions to produce alkyl fluoride, e.passing the remainder of said HF-enriched water-containing HF stream tosaid second stripping zone to remove at least some of the HF therefrom,and f. contacting at least a portion of the bottoms stream comprisingwater containing HF removed from said second stripping zone in areaction zone with an olefin under conditions which will produce analkyl fluoride.